This project is concerned with behavioral analyses of information transmission within the spinal somesthetic pathways. The approach is to obtain psychophysical thresholds before and after a variety of spinal lesions have been administered to monkeys. In addition, the investigations of monkeys are supplemented with human psychophysical investigations, using similar stimulus manipulations, to efficiently define interesting phenomena of somatosensory coding and to specify the degree to which the sensitivity of the monkeys corresponds to that of humans. The studies deal with major classes of somatosensory input: pain and touch. In the first instance, we are defining the importance of descending spinal pathways for pain control by morphine. The investigation of touch concentrates on temporal coding, to compliment our previous studies, which have emphasized spatial coding. We are testing the effects of spinal lesions on discriminations of touch duration. We administer multiple spinal lesions until deficits are obtained, and the extent of functional recovery following these spinal cord injuries will be carefully plotted. The results of this study will be related to human psychophysical observations and to recordings from single, peripheral fibers in monkeys, using the same stimulus manipulations.